What is even crazier is that the same is true of every Western European country.

Sub-Saharan Africa (and a few poor non-African countries such as Pakistan and Afghanistan) has very strong demographic momentum on its side, probably underrated by many. Africa already has around 3 times as many people under 40 as the whole of Europe, and the median age in Africa is less than half that in Europe. Fertility rates are significantly above replacement level now almost exclusively in African countries (+ a few Asian ones like Pakistan), so in Nigeria alone, more children are being born in a year than in the whole of Europe. In the DR Congo alone, more are being born than in the entire EU. By the end of this century, around 40% of the global population will probably be African. With such demographic momentum and international travel ever more affordable and accessible, the potential for migration from Africa will keep growing, and since most of the rest of the world is still a significantly better place to live than much of (especially sub-Saharan) Africa, even countries like Brazil, Serbia, and Georgia will face growing immigration pressures (they already are). In short, any country that isn't explicitly anti-immigrationist will experience mass Third World immigration.